A few years ago, Alistair McGowan went on holiday to Cornwall with his then girlfriend Ronni Ancona and her friends. "There were two gay guys, a writer and some of Ronni's girlfriends," he recalls, "and all had one thing in common – they couldn't care less about football." McGowan, on the other hand, had spent most of the year doing football-related gigs, and his head was filled with whether Rochdale would make the League Two play-offs, what Stenhousemuir's ground was like, and how great it was to be at Plough Lane when Wimbledon's Vinnie Jones grabbed Gazza's crown jewels. "I suddenly realised I had nothing to say to them."

It was, he says, a horrible epiphany. "I never thought of myself as an addict. I loved the idea of turning up to see a play on a Saturday night with a football programme from the afternoon in my pocket. I thought of myself as cultured, interested in a wide variety of things, but I was an addict. I just didn't realise."

McGowan reckons his addiction to football destroyed his relationship with Ancona, the other half of his double act on BBC1's the Big Impression, which ran from 1999 to 2002. She was the Nancy to his Sven, the Posh to his Becks, the Audrey Hepburn to his Cary Grant.

Off-screen, though, Ancona – whom McGowan had fallen for at a comedy club, describing her as "this sweet, lost-looking creature with the most beautiful clavicles I had ever seen" – felt suffocated by her partner's obsession with the game; his barmy need to study attendance figures on Ceefax, his inability to read a newspaper from front to back.

Even now, McGowan stuffs football references into his stand-up routines. During our interview, he does bang-on impersonations of the Aston Villa manager Martin O'Neill, commentator John Motson, and former Portsmouth manager Tony Adams in a post-match interview. "You don't need to know who Tony Adams is to appreciate this," McGowan says. "All you need to know is that whenever he did an interview, he always sounded as though he'd just been burgled."

I smile weakly at his impersonation, not because I didn't find it funny (I did) but because I worry for the mental health of someone who has let the beautiful game become an evil empire colonising every bit of his life, work and psyche. Surely, though, there must have been more to the break-up with Ancona than this infantile obsession?

"Well," retorts McGowan slightly reprovingly, fixing me with those huge eyes, "it typified the clash between us. We were opposites and that worked wonderfully: I became much wilder and more surreal in my comedy thanks to knowing and working with Ronni. But if we had stayed together, we would have killed each other – literally killed each other. And football would have been responsible for that."

This is where the Ancona-McGowan story gets reallyweird. They have just collaborated on a book called A Matter of Life and Death, Or How to Wean a Man off Football. What kind of an ex helps her former boyfriend over his football addiction? Especially when she's now married with kids, and her husband is – judging from what Ancona writes in the book – just as much of a football obsessive as her ex? Surely, despite the appeal of having a pair of household names on the dustjacket (a novel take on the two-for-one deal), she should have been trying to wean her husband rather than her ex?

Both Ancona and McGowan are aware their book risks confirming gender stereotypes that men who don't care about football and women who do may find insulting. No matter: after apologising for generalisations, they get on with offloading them in alternating chapters. "This is going to be difficult," McGowan writes about giving up football. "Nine months! And then I will, officially, be a girl!"

It was, in fact, a woman who unwittingly blighted McGowan's life with football, an elderly lady called Mrs Drury whom he met aged four on holiday in Barmouth, north Wales. "There's something quixotic in how we choose football teams we're doomed to stay with through the rest of our lives," McGowan says. "For me it was this nice lady from Leeds I met on holiday." After a week in Barmouth, young McGowan returned home to Evesham in Worcestershire a committed Leeds United fan. He even went to Leeds University in part because of its proximity to the club's Elland Road ground. Football, for McGowan, is a phenomenon that holds the world in place. "I recognise I have OCD about the game," he says, "and that in my interviews I come across as a seriously strange man, but football does keep me together."

'We no longer have the same cultural references'

Autumn marks McGowan's return from relative obscurity. For four years, he and Ancona were fixtures on British telly: the Mike Yarwood and Faith Brown of the new millennium. "My fame is a little like that of retired footballers; they get recognised on the street long after they don't get any work." He claims not to mind the relative dearth of TV gigs, having worked on several high-profile theatre productions in the West End and with the RSC. But he is clear about the reason for the declining clamour for his brand of mimicry: "multi-channel TV."

"The Big Impression worked because we had the same cultural references, but we're all watching different stuff now. I did, if I say so myself, a very good Dylan Moran [the Irish stand-up] around the time he was starring in Black Books. Then I did him for my mother and she said: 'Why are you doing Alan Rickman with an Irish accent?' TV has splintered, so where in the past I could expect my mother to know who Dylan Moran is, now I can't."

But do these socio-cultural changes mean the king of impersonators is obsolete? "Er, no," he says, fixing me with those huge eyes once more. "What it means is that when I impersonate someone, I have to assume most people won't know who it is. Nowadays it's about playing the percentages – some people will get my Tony Adams, some will appreciate my Colin Firth, others will like me doing Will Self as an X Factor judge."

That said, McGowan is, sensibly, diversifying his brand. He is now an author, a film star (thanks to his cameo as a sleazy Greek tour guide in the new romantic comedy Driving Aphrodite), and an actor as capable of playing Shakespeare as having balloons shoved down his trousers before going on stage to sing Money Makes the World Go Round (as he did in the West End production of Cabaret).

And he's a playwright. His first play, Timing, opens next month at the King's Head pub theatre in Islington and stars EastEnders' Dean Gaffney. "It's about a guy who meets his ex when they record an advert for a car that has Satnav as standard. It's about choice, about the acquisition of shite and about fatherhood. What is the right time for men to have children."

Curiously, on his return to stand-up last month, McGowan informed the press night crowd that his wife had just given birth to their third child, and duly received warm applause. It was a lie: he's currently unattached and childless. What was that about?

"I'd just done this incredible bit about snooker commentary, which had died, and then I get applause for nothing. I was pointing out how crazy it is that they react over a cultural shibboleth – me becoming a dad for the third time – and ignore what they're here to see." McGowan goes on tour next month for the first time in eight years, so if you're in the audience, try not to clap him for things he hasn't done.

But has Ancona's 12-step anti-football programme worked? It seems unlikely: McGowan's new stand-up routine remains riven with football arcana, and his acknowledgment at the back of the book includes the entire Leeds team from the early 70s. Still, he does believe that, with his ex's help, he has grown as a human being.

McGowan relates his pleasure in seeing Richard Strauss's opera Salome recently: "I saw it one night when I was working in theatre in Plymouth. Loved it – and not only because it was 90 minutes, the same length as a football match." Although that probably helped.